Vacuum/pressure sensors are commonly used in vehicle fuel tanks to monitor tank vacuum levels. When a vacuum/pressure sensor fails to operate properly, the sensor may indicate a constant vacuum level, even while vacuum is actually being increased (i.e., pressure is being reduced) in the tank. If a vacuum/pressure sensor fails to operate and its failure is not detected, the fuel tank can become damaged when excessive vacuum is applied. On the other hand, a properly operating vacuum sensor may register a constant vacuum level when a leak in the tank is sufficiently large to prevent vacuum in the tank from increasing.